Engine oil at 40oC flows over a 3mlong and 2mwide plate whos

Engine oil at 40oC flows over a 3-m-long and 2-m-wide plate whose temperature is maintained at 20oC with a velocity of 2 m/s. Determine the rate of heat transfer from the entire plate. Also determine the velocity and thermal boundary layer thickness.

Solution

Rate = k•A•(T1 - T2)/d

To solve this problem, we will need to know the surface area of the window. Being a rectangle, we can calculate the area as width • height.

Area = (3 m)•(2 m) = 6 m2.

We will also need to give attention to the unit on thickness (d). It is given in units of cm; we will need to convert to units of meters in order for the units to be consistent with that of k and A.

d =1 m assume

Now we are ready to calculate the rate of heat transfer by substitution of known values into the above equation.

Rate = (0.27 W/m/°C)•(6m2)•(40°C - 20°C)/(1 m)
Rate = 32.4 watt